Luminescence study study of oxygen vacancies in lanthanum hafnium oxide, La2Hf2O7

Luminescence properties of La2Hf2O7 have been measured for powdered samples prepared by solid state synthesis. These include photoluminescence excitation and emission spectra, x-ray excited spectra, luminescence decay profiles, and reflectivity spectra. The observed luminescence is attributed to self-trapped excitons and transitions involving energy levels of oxygen vacancies. The oxygen-vacancy-related luminescence consists of a broad band in the region 350-750 nm with a peak around 460 nm. The optical and X-ray excited emission spectra differ due to the more selective nature possible with optical excitation. The experimental results are in general agreement with spectroscopic properties predicted by theoretical electronic structure calculations of oxygen vacancy states by Liu et al. in 2007 [15]. The excitation and emission properties of the oxygen vacancy luminescence are shown to vary with the atmosphere and temperature of the synthesis process. (C) 2012 Elsevier B.V. All rights reserved.